Call it an exercise rut or a fitness threshold. Each of us can hit a wall when it comes to getting the most out of our workouts, so here’s advice from experts on how to break through.

Most of the recommendations about exercise are pretty straightforward — do something — anything — to get moving. Any activity is better than no activity, so simply putting the body in motion is what’s important. And there’s a good reason for the simplicity of that message — with one third of Americans not exercising at all, the easier the advice, the better.

But for those who follow those recommendations and get regular exercise, things could get a little more complicated. How far is too far when it comes to pushing your body? Overdoing exercise can lead to injuries, and may end up erasing all the benefits physical activity can have.

Our bodies are trained to adapt, so even if you run or bike every day, at a certain point, your body starts to coast. Your muscles don’t work as hard, your heart doesn’t beat as quickly, and you don’t breathe as heavily to pump oxygen to your cells. “When you hit a plateau, it is your body getting used to an activity and stimulus. You have achieved [your] body’s potential for that activity or that intensity,” says Scott Danberg, Director of Fitness, Pritikin Longevity Center & Spa. “When you started, you were getting all types of gains because you were at a different stimulus level. If you keep working at the same activity, it’s virtually impossible sometimes to keep moving up. It means you hit a status quo, which could mean you are still in great shape, but you have to start changing things to move forward.”

The same type of plateau occurs for weight loss–the initial effects of cleaning up a diet and picking up the exercise have a limit. You lose the most weight when you have the most to lose, and you tally up the most gains in fitness when you start by being relatively sedentary.

So how do you make sure that your exercise continues to work for you? In some cases, it may be as simple as switching up the equipment or your pace. If you typically use a treadmill, try increasing the speed or incline, or mix up the work out between fast and slow intervals.

Some fitness trainers also recommend changing workouts every four to six weeks to rejuvenate the body. Others say that the best litmus test is whether your workout challenges you — if you’re breathing hard and feel spent after exercising, then you’re reaping the benefits of that workout, whatever it might be.

And how do you know if you’re pushing too hard? While putting some stress on the body is required to improve fitness, Barbara Bushman, a professor in the department of kinesiology at Missouri State University says exercise overload can cause injury and frustration. “Typically for beginners, gradual increases in duration are recommended until the person is comfortable with longer exercise duration. Then the duration might be cut back a bit but the intensity increased. The [idea] is not to increase all areas at once,” she says.

Figuring out when to push, and when to pull back isn’t an exact science. Some people will hit their fitness plateau sooner than others, while some may only reach a few of these “levels,” as others cycle through ever-escalating challenges throughout their exercise experience. According to Bushman, 40% to 60% of a person’s physical abilities are genetically determined, so how much a body can take is determined by a combination of training and genetics. “Obviously everything is impacted by training level, but sometimes ability to perform [at a certain level] is not in someone’s DNA card,” she says.

Genes, for example, influence metabolic rates and body types, both of which contribute to fitness. So the ectomorph body type — small in stature — isn’t as conducive to building muscle mass as the mesomorph structure, which tends to include a larger frame, and is common in bodybuilding. People with the endomorph makeup are more heavy set, and have a slower metabolism, which means they tend to gain both muscle and fat faster and may need to work harder to burn off calories.

One of the best ways to find the most effective exercise plan for you — tailored to your body type and your fitness goals — is to periodically step back and do personal assessments. A doctor or trainer can help, or you can try these evaluations from the American College of Sports Medicine (ACSM). A good check-in should include your heart rate, body composition (that’s your ratio of muscle to body fat, flexibility and muscle strength. Tracking these measures while you exercise will not only tell you how far you have progressed, but let you know if you’ve either hit a plateau or are overdoing the workouts.